1. Technical Field
The present disclosure relates to an illumination system. More particularly, the present disclosure relates to an emergency illumination system which is able to automatically judge power interrupted situation.
2. Description of Related Art
Traditional emergency illumination device, such as an emergency exit indicator light incorporating LED (light-emitting diode), a wall-mounted LED emergency illumination, a wall-embedded LED emergency illumination, etc., is usually set up outdoors. Generally, when a power grid normally supplies power, the emergency exit indicator light incorporating LED keeps illuminating and an energy storage device therein is charged. When the power grid is interrupted, the emergency exit indicator light keeps illuminating until the energy storage device runs out of power supply. A wall-mounted LED emergency illumination and a wall-embedded LED emergency illumination are usually operated in a switch-off state, and they are switched on only when the power grid is interrupted.
Traditional emergency illumination system has a power grid detecting circuit. When the power grid normally supplies power, a charging device converts alternating current (AC) power to direct current (DC) power and charges the energy storage device in the emergency illumination device in a charging mode of constant current (CC) or constant voltage (CV) to maintain the power of the energy storage device. The energy storage device is electrically connected to a detecting circuit which is configured for detecting the state of the energy storage device, to avoid overcharging that causes damages to the energy storage device.
When the power grid is interrupted, a driving device in the illumination system cannot drive the light-emitting device to emit light. At the moment, the power grid detecting circuit outputs a control signal to control a switch element to be switched on such that the energy storage device can supply power to the light-emitting device and make the light-emitting device emit light.
From the above, traditional emergency illumination system can switch on the light-emitting device to emit light when the power grid is interrupted, because it has the power grid detecting circuit, the charging device, the detecting circuit, etc. However, since the traditional emergency illumination systems are all set up outdoors, indoor people still have to turn on flashlights or light up candles and are unable to switch on the emergency illumination system to illuminate when the power grid is interrupted.
Indoor light source is different from outdoor light source. Indoor light source has switches that users can operate the switches to switch on or off. If the indoor light source is combined with the traditional emergency illumination system, a wrong judgment easily happens, such as users switch off the indoor light source while the power grid detecting circuit in the emergency illumination system misjudges that the power grid is interrupted such that the energy storage device supplies power for the light-emitting device.
Therefore, it is desirable to set up the emergency illumination system indoors such that it can perform functions of illumination and be used to avoid that the emergency illumination system has false action when the power grid is interrupted.